How can I bake camera occlusion?
From what I gather, you want a pure black and white mask for face visibility.

If this is purely a geometric issue then a face (triangle) will either be visible or not. You could probably get away with a fairly accurate representation without needing any rendering.

With that in mind then you could just place the 3D viewport at the correct view angle with an orthographic camera.
With the border selection tool select all object faces. If you have the Limit Selection to Visible option enabled, occluded geometry wont be included.
You may have to triangulate your mesh beforehand if partial visibility is an issue, like if you have many NGons or highly distorted quads.

From then on, with the selection at hand you can do whatever you want with it.

Either give them a different material and OpenGL render the viewport, texture paint it, export its UV map and paint it in an external editing application, etc.



Alternatively if you require partial per-face visibility you could try texture painting it from a certain viewpoint.